With recent spiralling costs in fuel and a general movement toward fuel conservation, vehicle design has evolved to box-like configurations whether the vehicle is a small car, bus, or transport trailer. Box-like designs provide for maximum usage of space within the vehicle but, to their detriment, they do little in the way of providing streamlining for the vehicle and, the larger the vehicle becomes, the more detrimental the design is from the point of view of efficiently moving the vehicle through the air, particularly at highway speeds. Streamlining a vehicle by modifying its contours is expensive and impractical especially for large commercial vehicles.
Large, flat backed vehicles such as tractor trailer combinations and buses create a low pressure region adjacent its rearward surface during forward motion of the vehicle and this low pressure region in turn creates drag resulting in a higher consumption of fuel. In an effort to reduce this low pressure area and the resulting drag, numerous proposals have been made to provide some form of deflecting device for directing air flowing past the sides and top of the vehicles into the low pressure region to thereby reduce the effect of drag and consequently produce increased fuel efficiency for such large vehicles. However, the presently obtainable devices have not proven very satisfactory, the absence of any widespread use of deflecting devices being witness to this fact. The inherent disadvantages with conventional deflectors is that they are normally fabricated from numerous parts and for the large trailer operator, conventional devices have been unsuccessful due to the fact that they are easily broken or damaged when the trailer vehicle is backed into a loading dock or when the large swing doors are opened and pivoted 180 or more degrees to unload the contents.
Cab mounted deflectors have been in use for some time but while these reduce the amount of air that the front end of the trailer body has to contend with, they do little or nothing for the low pressure area at the back of the vehicle.